DEBUG_THREADS: Fix regression and lock tracking initialization problems.

This patch started with David Lee's patch at
https://reviewboard.asterisk.org/r/2826/ and includes a regression fix
introduced by the ASTERISK-22455 patch.

The initialization of a mutex's lock tracking structure was not protected
in a critical section.  This is fine for any mutex that is explicitly
initialized, but a static mutex may have its lock tracking double
initialized if multiple threads attempt the first lock simultaneously.

* Added a global mutex to properly serialize initialization of the lock
tracking structure.  The painful global lock can be mitigated by adding a
double checked lock flag as discussed on the original review request.

* Defer lock tracking initialization until first use.

* Don't be "helpful" and initialize an uninitialized lock when
DEBUG_THREADS is enabled.  Debug code is not supposed to fix or change
normal code behavior.  We don't need a lock initialization race that would
force a re-setup of lock tracking.  Lock tracking already handles
initialization on first use.

* Properly handle allocation failures of the lock tracking structure.

* No need to initialize tracking data in __ast_pthread_mutex_destroy()
just to turn around and destroy it.


The regression introduced by ASTERISK-22455 is the result of manipulating
a pthread_mutex_t struct outside of the pthread library code.  The
pthread_mutex_t struct seems to have a global linked list pointer member
that can get changed by other threads.  Therefore, saving and restoring
the contents of a pthread_mutex_t struct is a bad thing.

Thanks to Thomas Airmont for finding this obscure regression.

* Don't overwrite the struct ast_lock_track.reentr_mutex member to restore
tracking data in __ast_cond_wait() and __ast_cond_timedwait().  The
pthread_mutex_t struct must be treated as a read-only opaque variable.


Miscellaneous other items fixed by this patch:

* Match ast_suspend_lock_info() with ast_restore_lock_info() in
__ast_cond_timedwait().

* Made some uninitialized lock sanity checks return EINVAL and try a
DO_THREAD_CRASH.

* Fix bad canlog initialization expressions.

ASTERISK-24614 #close
Reported by: Thomas Airmont

Review: https://reviewboard.asterisk.org/r/4247/
Review: https://reviewboard.asterisk.org/r/2826/
........

Merged revisions 429539 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@429541 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 7 insertions, 40 deletions

diff --git a/include/asterisk/lock.h b/include/asterisk/lock.h
index 7741654a0..5e651600e 100644
--- a/include/asterisk/lock.h
+++ b/include/asterisk/lock.h
@@ -18,7 +18,7 @@
 
 /*! \file
  * \brief Asterisk locking-related definitions:
- * - ast_mutext_t, ast_rwlock_t and related functions;
+ * - ast_mutex_t, ast_rwlock_t and related functions;
  * - atomic arithmetic instructions;
  * - wrappers for channel locking.
  *
@@ -102,6 +102,12 @@
 
 struct ast_channel;
 
+/*!
+ * \brief Lock tracking information.
+ *
+ * \note Any changes to this struct MUST be reflected in the
+ * lock.c:restore_lock_tracking() function.
+ */
 struct ast_lock_track {
 	const char *file[AST_MAX_REENTRANCY];
 	int lineno[AST_MAX_REENTRANCY];
@@ -474,45 +480,6 @@ static inline void ast_reentrancy_unlock(struct ast_lock_track *lt)
 	}
 }
 
-static inline void ast_reentrancy_init(struct ast_lock_track **plt)
-{
-	int i;
-	pthread_mutexattr_t reentr_attr;
-	struct ast_lock_track *lt = *plt;
-
-	if (!lt) {
-		lt = *plt = (struct ast_lock_track *) calloc(1, sizeof(*lt));
-	}
-
-	for (i = 0; i < AST_MAX_REENTRANCY; i++) {
-		lt->file[i] = NULL;
-		lt->lineno[i] = 0;
-		lt->func[i] = NULL;
-		lt->thread[i] = 0;
-#ifdef HAVE_BKTR
-		memset(&lt->backtrace[i], 0, sizeof(lt->backtrace[i]));
-#endif
-	}
-
-	lt->reentrancy = 0;
-
-	pthread_mutexattr_init(&reentr_attr);
-	pthread_mutexattr_settype(&reentr_attr, AST_MUTEX_KIND);
-	pthread_mutex_init(&lt->reentr_mutex, &reentr_attr);
-	pthread_mutexattr_destroy(&reentr_attr);
-}
-
-static inline void delete_reentrancy_cs(struct ast_lock_track **plt)
-{
-	struct ast_lock_track *lt;
-	if (*plt) {
-		lt = *plt;
-		pthread_mutex_destroy(&lt->reentr_mutex);
-		free(lt);
-		*plt = NULL;
-	}
-}
-
 #else /* !DEBUG_THREADS */
 
 #define AO2_DEADLOCK_AVOIDANCE(obj) \